Tetragonopterus

Silva, Gabriel S. C., Melo, Bruno F., Oliveira, Claudio & Benine, Ricardo C., 2016, Revision of the South American genus Tetragonopterus Cuvier, 1816 (Teleostei: Characidae) with description of four new species, Zootaxa 4200 (1), pp. 1-46 : 10-11

Key to the species of Tetragonopterus

1. Eleven to 17 predorsal scales (Amazon, La Plata, Orinoco, Essequibo, Parnaíba and Jaguaribe rivers).................................................................................................... Tetragonopterus argenteus

1’. Seven to 9 predorsal scales...............................................................................2

2. Lozenge-shaped dark blotch on caudal peduncle (Rio Jari)................................. Tetragonopterus carvalhoi

2’. Rounded or oval-shaped dark blotch on caudal peduncle.......................................................3

3. Three and a half scale rows between lateral line and pelvic-fin origin.............................................5

3’. Four and a half to 5.5 scale rows between lateral line and pelvic-fin origin........................................4

4. Presence of longitudinal dark stripes on the lateral surface of the body (Corantijn and Marowijne basins, Rio Jari and Rio Paru )................................................................................... Tetragonopterus rarus

4’. Absence of longitudinal dark stripes on the lateral surface of the body ( Essequibo, Marowijne, Oyapock and Paru rivers)..................................................................................... Tetragonopterus georgiae

5. Seventeen to 20 gill-rakers on the lower limb of the first gill arch................................................ 6

5’. Eleven to 15 gill-rakers on the lower limb of the first gill arch..................................................7

6. Subsuperior mouth, 5–6 thin teeth on dentary, 2–4 teeth on the maxilla (Tocantins-Araguaia system).................................................................................................... Tetragonopterus anostomus

6’. Terminal mouth, 4 robust teeth on dentary, 0–2 teeth on the maxilla (Rio Araguaia).......... Tetragonopterus araguaiensis

7. Five to 6 thin and sharp teeth on dentary....................................................................8

7’. Four relatively robust teeth on dentary.....................................................................10

8. Seven scale rows between dorsal-fin origin and lateral line (Tocantins-Araguaia system)....... Tetragonopterus denticulatus

8’. Six scale rows between dorsal-fin origin and lateral line.......................................................9

9. Two conspicuous humeral marks (upper Rio Tapajós)...................................... Tetragonopterus juruena

9’. A single conspicuous humeral mark (Rio Xingu).................................... .. Tetragonopterus kuluene sp. n.

10. Up to 6 teeth on maxilla............................................................................... 11

10’. Seven to 8 teeth on maxilla (middle Rio Tapajós).................................... Tetragonopterus ommatus sp. n.

11. Eleven to 17 olfactory lamellae, 4 thin teeth on dentary (São Francisco, Paraguaçu and Itapicuru rivers of northeastern Brazil)........................................................................ Tetragonopterus franciscoensis sp. n.

11’. Eighteen to 40 olfactory lamellae, 4 robust teeth on dentary (Amazon, Orinoco and Guianas)...... Tetragonopterus chalceus